enum School {
    principal,
    teacher,
    student
};

enum Company {
    chairman,
    manager,
    employee
};

int main()
{
    School x = student;
    Company y = manager;
    bool b = student >= manager;    // 不同类型之间的比较操作
    b = x < employee;
    int y = student;                // 隐式转换为int
}